Rotary impact motor

ABSTRACT

IN A ROTARY IMPACT MOTOR FOR POWER DRIVEN FASTER SETTING TOOLS AN IMPACT DOG IS ARRANGED IN A HAMMER BODY PIVOTALLY ABOUT AN AXIS SPACED FROM BUT PARALLEL WITH THE AXIS OF ROTATION OF THE HAMMER BODY. THE IMPACT DOG TAKES RESPECTIVELY IMPACT AND RELEASE POSITION WITH RESPECT TO A CAM FLANK ON AN ANVIL WHICH ANVIL IS COAXIAL WITH THE HAMMER BODY. THE CAM FLANK HAS THE DUAL FUNCTION OF PROVIDING AN IMPACT SURFACE FOR THE IMPACT DOG AND A CAM SURFACE COOPERATING WITH THE PORTION OF THE IMPACT DOG LEADING IN THE ROTATIONAL DIRECTION FOR PIVOTING THE TRAILING PORTION THEREOF TO IMPACT POSITION AGAINST THAT VERY SAME FLANK.

- Sept.2l, R Q 3,605,931

, v ROTARY IMPACT MQTOR Filed June 9; re'ro 2 Sheets-Sheet 1 I4 f l6 I23 Fig-l 1/ p 21, 1971 K. G. KARDEN 3,606,931

ROTARY IMPACT MOTOR 2 Sheets-Sheet 2 Filed June 9, 1970 United StatesPatent 3,606,931 ROTARY IMPACT MOTOR Karl Gosta Karden, Nacka, Sweden,assignor to Atlas Copco Aktiebolag, Nacka, Sweden Filed June 9, 1970,Ser. No. 45,047 Claims priority, application Sweden, June 19, 1969,

8,807/ 6 Int. Cl. B25d 15/00 US. Cl. 173-935 Claims ABSTRACT OF THEDISCLOSURE In a rotary impact motor for power driven fastener settingtools an impact dog is arranged in a hammer body pivotally about an axisspaced from but parallel with the axis of rotation of the hammer body.The impact dog takes respectively impact and release position withrespect to a cam flank on an anvil which anvil is coaxial with thehammer body. The cam flank has the dual function of providing an impactsurface for the impact dog and a cam surface cooperating with theportion of the impact dog leading in the rotational direction forpivoting the trailing portion thereof to impact position against thatvery same flank.

The invention relates to a rotary impact motor of the kind used inconnection with fastener setting tools, impact wrenches and the like. Insuch application is formerly known a type of rotary impact motor withimpact action in both rotational directions thereof against therespective of two cam flanks on a rotatable anvil, in which a hammerbody is rotatably carried coaxially with respect to the axis of rotationof the anvil, and an impact dog is journalled pivotally on the hammerbody about an axis spaced from but parallel with said axis of rotationfor taking respectively impact and release position with respect to thecam flanks, cam surfaces cooperating with the impact dog being arrangedon the anvil for pivoting the impact dog towards the impact position,and a drive element being in engagement with the impact dog for rotatingthe latter together with the hammer body and arranged for pivoting theimpact dog towards the release position.

In such rotary impact motors there is normally had, in immediatesequence to the impact, a rebound of the hammer and the impact dog whichcauses that the angle of acceleration for the next impact is increasedand for example in connection with motors working on one impact perrevolution can exceed 360 degrees. As a result thereof the impact motorproduces a steep rise of the tightening torque applied per impact. Intightening operations in which the final tension of the fastening meanshas to lie within relatively narrow limits, for example in certain nutand screw setting applications, this is apt to cause large deviation ofthe final tension in a group of fastening means tightened under similarconditions and renders diflicult the application of simple torquecontrol means which can be had for example by variable throttling of theair pressure of the air entering into the drive motor of the impactmotor.

It is an object of the invention to provide a rotary impact motor havinga substantially more level characteristic .curve for the torque-timeparameters so that control sufficiently exact for practical use may behad of the final torque solely by adjustment of the pressure enteringinto the drive motor of the impact motor.

For the above and other purposes there is according to the inventionprovided a rotary impact motor with impact action in both rotationaldirections thereof comprising a housing, a rotatable anvil in saidhousing, opposed cam flanks on said anvil, a hammer body rotatablycarried in said housing coaxially with respect to the axis of rotationof said anvil and around said cam flanks thereof, an imice pact dogpivotally journalled on said hammer body about an axis spaced from butparallel with said axis of rotation for taking respectively impact andrelease positions with respect to said cam flanks, a recess on saidimpact dog facing said anvil and defining opposed portions on saidimpact dog respectively leading and trailing in the rotational directionthereof, the flank that meets the rotation of said impact dog duringrotation of said hammer body relative to said anvil cooperating with theleading portion of said impact dog for pivoting the trailing portionthereof to impact position against that very same flank, and rotatabledrive means in said housing in operative engagement with said impact dogfor rotating it together with said hammer body and for pivoting saidimpact dog towards said release position.

By this novel arrangement the impact dog at the moment of impact isgiven an impulse to roll over the cam flank receiving the impact so thatthe rebound is eliminated. This over-rolling produces, as a matter offact, a reverse torque by reason of the portion of the impact dogleading in the rotational direction hitting against the anvil beyond theflank against which the impact was applied in the first place and thusdelivering a torque impulse in a direction opposite to the drivedirection, replacing the rebound. The reverse torque is an advantage forexample during threading operations in which experience shows that thereverse torque pulses cause breaking of the chips and thus are apt toimprove the cutting effect.

The above and other purposes of the invention will become obvious fromthe following description and from the accompanying drawings in which anembodiment of the invention is illustrated by way of example. It shouldbe understood that this embodiment is only illustrative of the inventionand that various modifications thereof may be made within the scope ofthe appended claims.

In the drawings FIG. 1 shows a longitudinal section through an impacttool including a rotary impact motor according to the invention. FIG. 2is a cross section on the line 2-2 in FIG. 1. FIG. 3 is a partialsection seen on line 3-3 in FIG. 1. FIG. 4 is a cross section throughthe rotary impact motor in release position after the delivery of animpact and seen on the line 4-4 in FIG. 1. FIGS. 5-8 show variousrelative positions of the parts in FIG. 4 up to an impact beingdelivered in the impact position shown in FIG. 8.

The impact tool in FIG. 1 is an impact wrench including a back piece 10provided with a handle 11 and a front piece 12. The front piece 12encloses the rotary impact motor or impact clutch and is provided with acentral forward opening 13 through which a rotatable anvil 15 projects.The anvil 15 is journalled in a roller bearing 14 carried by the frontpiece 12 In the back piece 10 is aflixed a rotation motor 20 preferablya reversible pneumatic or electric motor having a rotor 16 arrangedtherein. The rotor 16 in the case of a pneumatic motor has radialgrooves taking up vanes 17 and is rotated in the usual way by the vanes17 through actuation of compressed air delivered to the motor 20 andsuitably introduced through the handle 11. The motor 20 is controlled bya throttle valve, not shown, and by a conventional reversing slide 18.

At the ends thereof the rotor 16 is journalled in the back piece 10 inroller bearings 22 and 23 and the forward end thereof is extendedthrough the roller bearing 22 and carries parallel axially extendingsplines 24, FIG. 2. The rotor 16 has a forward axial bore 19 whichrotatably takes up a guide pin 21. The forward end of the anvil 15carries a polygonal end portion 25 for the application of a socketwrench, not shown. At the roller bearing 14 the anvil 15 has acylindrical portion 26 which within the front piece 12 passes over intoa radial cam 27. The rear end of the anvil 15 is provided with an axialbore 28 which takes up the pin 21 with a press fit, the rear end havinga cylindrical reduced portion 29 which is surrounded rotatably by acylindrical drive element 30. The drive element 30 has a partlycylindrical recess 32 at the periphery thereof and is by axial grooves31 at a rear hub portion thereof in engagement with the splines 24, FIG.2, of the rotor 16.

A hammer body 35 is coaxially rotatably journalled about the anvil andsits by way of a forward hub portion 36 rotatable on the cylindricalportion 26 of the anvil 15 behind the roller bearing 14. The hammer body35 is provided with a rotation cavity 37 coaxial with the axis ofrotation thereof which cavity surrounds the radial cam 27 and permitsfree rotation of the latter relative to the hammer body 35 within thecavity 37. Out into the rotation cavity 37 there opens a journallingcavity 38 provided by a cylinder surface and intended for an impact dog40 which by means of a cylindrical back portion 39 along the entirelength thereof is slidably supported by the cylinder surface of thejournallin'g cavity 38 pivotally about an axis 33, FIG. 4, coaxialtherewith, falling within the rotation cavity 37, and in parallelrelation to the axis 34 of rotation of the hammer body 35. The rotationcavity 37 rearwardly thereof is terminated by an enlarged cylindricalportion 41 which rotatably takes support against the periphery of thedrive element 30.

The radial cam 27 of the anvil 15 is single-lobed relatively narrowperipherally and is with respect to a diametrical plane symmetricallybordered by two opposed cam flanks 42, 43 which pass over into acylindrical central cam ridge 44 with the centre of curvature in saiddiametrical plane. The impact dog 40 is recessed somewhat similarly toturbine blade shape with internally flattened limbs and the recessthereof has on the one hand a concave cylindrical middle surface 45 withthe same radius of curvature as the cam ridge 44 and coaxial with thejournalling cavity 38, and on the other hand flat sides 46, 47 divergingoutwardly from the middle surface 45, the sides 46, 47 and the middlesurface 45 being intended for impacting against the respective camflanks 42, 43 and the adjacent portion of the cam ridge 44.

The forward end of the impact dog 40 is supported pivotally in thejournalling cavity 38 by a pivot portion 48, FIG. 3, projectingrearwardly from the hub portion 36 into the journalling cavity 38, thepivot portion 48 having the same radius as the middle surface 45 of theimpact dog. The rear end of the impact dog 40 has a central extension49, FIG. 2, which falls into the cylindrical recess 32 of the driveelement 30 and is in camming engagement therewith.

Let it be supposed that the rotor 16 in operation rotates the rotaryimpact motor and thereby the anvil 15 thereof in clockwise direction bythe driving connection consisting of the splines 24 and the grooves 31and that the polygonal end portion of the anvil 15 through a socketwrench, not shown, transmits the rotation to a threaded fastener. If theparts of the rotary impact motor are in the impact position shown inFIGS. 2 and 8, the middle surface 45 and side 46 of the impact dogrecess will remain in impact position as long as the screw rotateseasily and in engagement with the flank 42 of the radial cam 27 and theadjoining part of the cam ridge 44. The rotation of the drive element istransmitted at the recess 32 thereof and at the extension 49 of theimpact dog 40 to the impact dog 40 and thence via the radial cam 27 tothe anvil 15, the socket wrench, and the fastener. Thus the impact dog40 transmits the rotation to the radial cam 27 via the portion thereoftrailing in the rotational direction, in which portion the side 46provides the main driving surface. It is true that the drive element 30during driving strives to turn the impact dog 40 over the cam ridge 44to the released position. This is so because the driving engagementbetweeen the cylinder surface of the recess 32 and the extension 49,FIG. 2, which engagement takes place radially at opposite side of thepivoting axis 33 of the impact clutch with respect to the axis 34 ofrotation of the hammer body 35, in lever-like manner strives to turn theimpact dog 40 about the axis of the cam ridge 44 which in the impactposition shown, FIG. 8, coincides with the pivotal axis of the impactclutch 40 and the geometrical axis 33, FIG. 4, of the journalling cavity38. Through friction between the impact clutch 40 and the radial cam 27these parts, however, remain in engagement with each other substantiallyin the position shown in FIG. 8 so that the fastener is rotatedcontinuously until it has been screwed down and the resistance torotation increases.

At sufiiciently large rotational resistance the anvil 15 stops while therotor 16 forces the drive element 30 to continue its rotation. Thiscauses the impact dog 40, due to cam action between the cylinder surfaceof the recess 32 and the extension 49 of the impact dog 40, to be swungover the radial cam 27 from the impact position in FIGS. 2 and 8 torelease position in FIG. 4. The side 47 of the impact dog leading in therotational direction is now pivoted to take support against the radialcam 27 of the anvil 15 at and beyond the flank 43 and the leading edgeof the side 47 is successively forced to slide around the radial cam 27while the hammer body 35 in an accelerated movement is rotated aroundthe anvil 15 by the drive element 30. The acceleration course isillustrated in the FIGS. 47. Near the end of the acceleration cycle theside edge of the impact dog 40 leading in the rotational direction runsup on the cam flank 42 and the cam ridge 44, FIG. 6, of the radial cam27, which causes a reverse swinging of the impact dog 40 about itspivotal axis 33 followed by a simultaneously performed forward turningand still further acceleration of the hammer body 35 in the rotationaldirection additional to the acceleration produced by the drive element30. Immediately thereafter the impact dog 40, FIG. 8, hits with its side46 trailing in the rotational direction and the adjoining middle portionthereof against the cam flank 42 and the cam ridge 44 so that thekinetic energy of the hammer is delivered to the anvil 15 by way of arotational impact which is transmitted to the socket wrench and thefastener.

At impact, FIG. 8, there is normally generated no reverse angularmovement due to rebound of the hammer body 35 and the impact dog 40relative to the radial cam 42 of the anvil 15. In direct sequence to theimpact the impact dog, as a matter of fact, is pivoted over the ridge 44of the radial cam 27 to the position shown in FIG. 4, and the recoilupon impact is thus transformed into an angular acceleration of theimpact dog 40, the latter delivering its kinetic energy in the form of arearwardly directed impact by means of the side 47- of the impact dog 40leading in the rotational direction and against the cam flank 43, FIG.4. At this instant there is generated a momentary reverse torque.Thereupon the next acceleration and impact courses are performed inanalogy with the above described cycle until the desired tighteningtorque has been reached in the fastener. Thanks to the fact that theacceleration angle of the rotary impact motor remains substantiallyuninfluenced by rebound at the moment of impact, one receives an evenlyand only gradually in creasing tightening torque in the screw so that aneffective torque control can be had solely by the adjustment of the airpressure before the vanes 17 of the rotor 16.

The symmetrical design of the rotary impact motor assures correspondingimpact action at rotation in counterclockwise direction. Now the impactsare delivered by the side 43 of the impact dog 40 trailing in therotational direction and against the flank 43, while the portion of theimpact dog at the outer edge of the side 46 leading in the rotationaldirection causes turning of the impact dog to impact position.

I claim:

1. A rotary impact motor with impact action in both rotationaldirections thereof comprising a housing, a rotatable anvil in saidhousing, opposed cam flanks on said anvil, a hammer body rotatablycarried in said housing coaxially with respect to the axis of rotationof said anvil and around said cam flanks thereof, an impact dogpivotally journalled on said hammer body about an axis spaced from butparallel with said axis of rotation for taking respectively impact andrelease positions with respect to said cam flanks, a recess on saidimpact dog facing said anvil and defining opposed portions on saidimpact dog respectively leading and trailing in the rotational directionthereof, the flank that meets the rotation of said impact dog duringrotation of said hammer body relative to said anvil cooperating with theleading portion of said impact dog for pivoting the trailing portionthereof to impact position against that very same flank, and rotatabledrive means in said housing in operative engagement with said impact dogfor rotating it together with said hammer body and for pivoting saidimpact dOg towards said release position.

2. A rotary impact motor according to claim 1 in which said cam flanksform the opposite sides of a single-lobed radial cam on said anvil, saidradial cam forming a cam ridge falling concentrically into said recessof said impact dog in the impact position thereof and being symmetricwith respect to a diametrical plane through the axis of rotation of saidanvil and said cam ridge.

3. A rotary impact motor according to claim 2 in which said hammer bodyis provided with a cylindrical rotation cavity surrounding said radialcam and a journalling cavity opening out into said rotation cavity andbordered by a cylinder surface coaxial with the pivotal axis of saidimpact dog, the back portion of said impact dog during pivotal movementthereof being slidably supported by said journalling cavity, and thegeometrical axis of the cylinder surface of the journalling cavity beingdisposed within the rotation cavity and in impact position of saidimpact dog falling radially within said cam ridge of said radial cam.

4. A rotary impact motor according to claim 3 in which said cam ridge iscylindrical and in impact position of said impact dog is substantiallycoaxial with the geometrical axis of said journalling cavity, the recessof said impact dog comprising a central cylindrical middle surfacecoaxial with said geometrical axis of said journalling cavity and sidesdiverging outwardly therefrom.

5. A rotary impact motor according to claim 1 in which said drive meansis a drive element in camming engagement with said impact dog radiallyat opposite side of the pivotal axis thereof with respect to the axis ofrotation of said hammer body and anvil.

References Cited UNITED STATES PATENTS 2,343,596 3/1944 Van Sittert etal. 173-935 2,768,546 10/1956 Amtsberg 173-935 3,129,796 4/1964 Karden17393.5 3,179,219 4/1965 Karden 17.3-93.5 3,533,479 10/1970 Madsen eta1. 17393.5

JAMES A. LEPPINK, Primary Examiner

